I bought this because I'm familiar with a 3/4" forstner bit " wanted to drill deep holes. I carefully checked that the dimensions of the barrel that the drill is in are 3/4 inch. Perfect! With a diameter of 3/4 inch, it would not only slide into that drill crazy hole, but also help keep the hole vertical. It will not fit in the hole created by the 3/4" bit. A good idea spoiled by frivolity sits in a drawer, waiting for either a bigger hole or homebrew adjustments.